My novel process may be used to preserve a great variety of proteic foodstuffs. One, commercially important application is the manufacture of fish meal for animal consumption.
Based, for example, on tests involving lamb breeding, the results obtained by feeding fish meal as heretofore prepared were definitely inferior to those expected based on the amount of nitrogen reported by previous tests of fish meal. This was due to the very low digestibility of such meal, to its high content of toxic amines, and to its high bacterial counts.
In reviewing the processes of manufacturing of fish meal heretofore employed, I found that the low digestibility is due to:
1. the fact that the making of the product involves dehydration by application of a direct flame in rotary furnace; or
2. that this is done at a very high temperature in a steam dehydrator (with the further disadvantage that the meal obtained by this process has a highly increased bacterial count); and
3. that meal obtained by the so-called "instant drying process" also suffers a very high thermal treatment which lowers digestibility.
Furthermore, in some heretofore employed processes, the foodstuff is polluted with exhaust gases from internal combustion engines, this being added to the pollutants already in the fish because of the state of decomposition or decay it normally has when it is manufactured into meal.
In an effort to overcome the disadvantages of the foodstuff preservation methods just described, a test was made in Teacapan, State of Sinaloa, Mexico of a modification of the Uruguayan system of fish siloing called "BIOPEZ" which, in turn, is a modification of the Swedish system designed by Virtanen. The tested process involves a bacterial promoted, hydrolysis or fermentation of fish, producing a paste which, while difficult to transport, can be delivered in tank trucks to distribution stations or to the consumer.
More specifically, the fish are ground and then transferred to cement vats. To each 100 kilograms of ground fish is added 20 kilograms of concentrated yeast (Cndomycetaceae subfamilia, Saecharomycetoideae genus, Saccaromyces isolated from the body of sea-bass (Micropogon opercularis)). The ingredients are intimately mixed, and the mixture is agitated three times a day for 6-7 days, after which fermentation is completed. The paste retains its original volume and has a dark brown color with a pleasant odor similar to that of dry figs and a firm consistency. To preserve the preparation for extended periods, 20 kilograms of 50% sulphuric acid are added to each 100 kilograms of paste giving a pH of 4.0-4.5. The paste may be directly fed to the animal without neutralizing it.
While an improvement over the other processes described above, the Mexican (modified Uruguayan) process just discussed is still not satisfactory as far as the quality of the product is concerned.
Another heretofore available technique for preserving protein foodstuffs is the process of "formol sprinkling" used in Peru. However, this only protects the product for a few hours, and it is generally inapplicable. Furthermore, the 37.2% by weight formaldehyde used in the process lowers the digestibility of proteins, increasing costs. Furthermore, formaldehyde acts superficially, not penetrating to the viscera of even small fish such as anchovies; and the amounts which are used are critical.
In short, to obtain adequate protein heretofore required the use of a fresh product; the only practical manner to achieve this to now has been to protect the material against decomposition by refrigeration. This may be done with ice as is done with shrimps and in the U.S. Gulf zone to manufacture fish meal or by using refrigerated brine as is done in Peru. Economically, neither of these two techniques is feasible for foodstuffs intended for consumption by animals.